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How to build a roof over on-site caravan?

LizzieCro

Hi Everyone,

I'm looking for any advice about what to use on the annexe of my onsite caravan. The annexe roof leaks, and I've learned from previous experience the simplest, most effective solution is to roof over the existing structure. Previously (on another onsite van I owned) I installed a roof of corrugated iron over treated pine battens/rafters, attached directly onto the roof, but in this instance I'm unable to do so without a lot of additional costs (barge boards, fascia, guttering and down pipes). So I'm looking for the most cost effective method of covering the roof. Tropical rooves don't interrupt all the ingress of water, so that's not an option.

The existing roof is made of sandwich panels, often referred to as refrigeration panels. (They're basically just 30mm polystyrene clad on both sides with thin aluminium). It's a sloping roof, not gabled or complicated in any way. I'm thinking maybe just high pressure washing the roof, then adding another sealed layer of the same panels might be do-able. Alternatively, are there any flat sheet metal panels which might be able to be installed over it? I could use an adhesive sealant like SikaPro, plus screws to attach it. I'm sure there's other options I don't know about, and that's why I'm asking here.

If anyone has any experience with this sort of thing, or roofing in general, I would be very grateful for your suggestions.

Thanks very much.

This isn't the van in question, but the roof looks much the same

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EricL

Hello @LizzieCro

Placing a form of roofing sheet over your existing roof is a sound idea. However, before attempting that proposed solution, I would like to suggest looking at applying https://www.bunnings.com.au/crommelin-1l-exterior-grade-brushable-waterproofer-1l_p0961573 . This can cover existing gaps and joints on the roofing panel as well as the screw heads which can also be a source of the leak. It would generally speaking be an easier repair option.

My best advice would be to pressure wash the roof surface if possible and use https://www.bunnings.com.au/30-seconds-5l-outdoor-cleaner-concentrate_p4461755 to thoroughly clean the surface before applying the waterproofing agent.

Let me call on our experienced members @Dave-1, @Nailbag, @Noyade, @twocutekelpies and @daniknight4 for their recommendations.

Please remember to wear personal protection such as gloves, goggles and a mask. If you are using a ladder, please have a quick look at this safety guide -

https://www.workshop.bunnings.com.au/discussion/89114/how-to-use-ladders-safely

If you need further assistance, please let us know.

Eric

Dave-1

Good Evening @LizzieCro

I am afraid I have not had a lot of experience with installing any type of sheeting over an existing structure :/ I would have the weight in the back of my mind and try to factor that in. I do like the idea of a waterproof paint/material that @EricL has suggested.

Dave

LizzieCro

Hi @EricL,

Thanks for your suggestions. Through sad experience, and having owned multiple onsite vans, I know that re-sheeting the annexe roof is by far the least painful and ultimately better way to go. Because the onsite vans are so old, some 60 years old, many, many previous owners have tried to resolve the leaks in the annexe rooves. Few who have tried have had any idea of what they're doing, so the initial prep work wasn't done, the layers of sealant are usually just the wrong type for the job, then that's compounded by the next owner adding more and more sealants on top. For me, this is a 'been there, done that' sort of thing, as I have, on other vans, tried more passive and inexpensive solutions first, always battling with what came before. I'm very confident re-sheeting is the best way to go. Everything you suggested makes sense if the roof had never been touched before, but unfortunately that isn't the case with old annexe rooves. I have used Crommelin's before with great results, but only on the actual caravan rooves, not the annexe. I've just discovered the extent of the many, many layers of products on the roof, and there is no way that is coming off. My commitment to it just isn't that great!

Hi @Dave-1,

Thanks for replying. The weight won't be an issue as it will be distributed right across the annexe, including over the exterior walls. I've installed a corrugated roof previously over battens, and it didn't make any negative impact.

Thanks gents. Hopefully someone will know of some sort of flat sheeting I can use.

MitchellMc

Hi @LizzieCro,

You mention flat sheets. Have you considered Twinwall polycarbonate?

Mitchell

Noyade

My father had a caravan - never went anywhere with it - so he built essentially a 'carport' around it with corrugated roofing and gutters. And it extended beyond the caravans dimensions so rain never touched the roof - lasted 50 years. To me, that image above looks like a contoured 'roof rack' that won't keep all the rain out? I'm not sure why contoured - looks complicated - aesthetics?

R4addZ

Hi @LizzieCro

I think we need pictures of your problem area as the picture shown shows a cover over a caravan but you keep referring to roofing over the annexe. It would make it easier for us to appreciate the real issue and the structure we need to apply a solution to.

MitchellMc

Hi @R4addZ,

I suspect it's the sloped roof over the annex to the side of the caravan that @LizzieCro is referring to. They are typically foam-cored panels that are notorious for leaking at the joints between panels. I'm sure they'll be able to clarify for us, though.

Mitchell

R4addZ

@MitchellMc

Lizzie states….

This isn't the van in question, but the roof looks much the same

I was concerned about suggesting any solution for a structure sight unseen. just because it looks like that doesn't mean the structure is as sound.

I suppose the other question is that if it is just a flat roof like this, why not just re-roof it?

LizzieCro

Thanks very much everyone.

Hi @Noyade , I imagine the reason the tropical roof over the van is contoured to slope down at each end is so water runs off more easily. Some tropical rooves are just sloped to one end, others are bowed like this. You're very correct, about rain still getting under that. Everyone tells me this is the solution to a leaking caravan roof. Not so, as rain doesn't generally fall vertically. Council regulations forbids these tropical rooves from extending beyond the dimensions of the van, and the park managers forbid anyone from enclosing the sides. But anyway! We're discussing the annexe, not the caravan.

Hi @R4addZ, the annexe is the skillion roof to the right of the caravan (any caravan) in the image. It needs no more explaining really. As mentioned previously, it's a polystyrene slab sandwiched between two thin layers of aluminium. Its structural integrity is created by the thick H-shaped aluminium channels which join the panels together. These channels are usually the source of most of the leaks.

Hi @MitchellMc , the structure is entirely sound. I've walked across it before with no ill effect to the roof. On a previous onsite annexe I have installed battens across the whole roof and added corrugated roofing, so I know the structure can handle the extra weight. My park managers wouldn't approve me doing this at this park, hence why I'm after some sort of flat panelling to be as inconspicuous and streamlined as possible. Why not just re-roof it? If you mean remove and replace the existing refrigerator panels, well this would involve greater cost, with the panels, installer and electrician, and more work. I would then have to undertake interior repairs, sealing, sanding and painting. This is why I'm wanting to roof over it, attaching the new roof to the existing roof as closely as possible so there can be no further water ingress. This will be the easiest and cheapest way to deal with the problem. I really like your suggestion of the twinwall polycarb. That's exactly the sort of thing I had in mind. I'd completely forgotten there was an exterior product I could use, and had no idea it came in such long lengths. Thanks very much for the suggestion. Do you think I could use SikaPro to adhere it, plus screws into the alumium joiner chanels?

EricL

Hello @LizzieCro,

Sikaflex Pro should work nicely on the twinwall polycarb roofing. My best advice is to pre-drill the sheet for ease of attachment when you get to the roof. I propose applying https://www.bunnings.com.au/selleys-290ml-grey-storm-sealant_p0130874 on the screw heads for a watertight seal.

I also recommend having a quick look at this safety guide - How to use ladders safely.

Eric

LizzieCro

Thanks @EricL. Sikapro is a very good sealant as well as adhesive, so I'd probably just stick with that. I'd have to run the polycarb lengthwise over the roof, I think, so each length gets screwed down. Otherwise, because the polycarb panels are narrow, they wouldn't all be screwed down into the joiners. Hmm, that might be more likely to leak in between the joins. Guess I'd just have to run sealant down each join too??

EricL

Hello @LizzieCro

I was also going to suggest perhaps using https://www.bunnings.com.au/fix-it-fast-repair-tape-50mm-x-5m-aluminium-waterproof-flashing-tape_p0592331 to seal all the edges of the polycarb sheeting. The flashing uses a butyl adhesive that bonds to almost any surface. It's an excellent option if you are looking for an alternative to sealers.

Eric

R4addZ

Hi @LizzieCro

If the roof can take your weight in isolated areas at one time, then why not just put a tin roof directly over it! the weight per square metre would not be greater than yours and could be screwed directly on to the existing structure!

LizzieCro

Thanks @EricL that sounds a very good idea. I know the product you're referring to and it'd be ideal.

@R4addZ yes, that's what I've done previously. It's the obvious solution but the park owners won't permit it in this park, unfortunately. This is why I'm trying to find a less conspicuous, streamlined solution.

R4addZ

Hi @LizzieCro

Have you considered using bitumen laid roofing felt over the whole roof? It is used on flat roofs and even as a damp proof course in some walls.

LizzieCro

Hi @R4addZ ,

Thanks for the suggestion. If the roof had never been 'fixed' by the many previous owners over the past 40 or 50 years, that'd possibly be an option. However, given it has every imaginable waterproofing solution and compound applied badly and incorrectly over everything again and again and again, the effort of removing all those layers then ensuring the adhesion of the bituminous compound simply wouldn't be worth it. If I went to all that work and cost, then the new fix didn't work… well. Been there done that! As I said, I learned from experience the most time, labour and cost effective way to solve this issue is to somehow sheet over the whole roof.

I did try and get an annexe building company to sheet over it, but sadly they only roof, not roof over rooves. They believe if I did that the structure would be non-compliant with council.

R4addZ

Hi @LizzieCro

Unfortunately it sounds like you are going to have to re roof it